Dynamic thermal analysis is imperative to ensure the reliability of chiplet-based 2.5D integrated systems. However, conventional simulation techniques typically incur high computational cost, especially in transient scenarios. In this paper, we propose a domain transformation and decomposition method (DTDM) to perform composable thermal modeling and simulation with high efficiency and accuracy. Temporally, the DTDM expands the time-variant temperature response into a sum of weighted Laguerre polynomials (WLPs). By leveraging Galerkin’s method and the orthogonality of WLPs, the heat conduction equation is transformed from the time domain to the Laguerre domain, thus breaking through the bottleneck of conventional marching-on-in-time approaches in terms of stability and efficiency. Spatially, the DTDM decomposes the system into multiple composable modules (CMs) according to the structural and functional characteristics. For each CM, a novel Laguerre-based macro-model is constructed to represent its internal heat transfer properties by mapping the relationship between the temperature and heat flux at the interface. Finally, the CMs are assembled together as a complete system by treating the macromodels as equivalent thermal boundary conditions, which reduces the computational complexity in both the temporal and spatial domains and thus facilitates efficient transient simulation. Moreover, since the resulting Laguerre-based macromodels are reusable in different system configurations, the DTDM is particularly suitable for composable thermal modeling and simulation. Numerical experiments on typical 2.5 D chiplet-based integrated systems show that the proposed method delivers a $485 \times$ speedup compared to the commercial software, while maintaining a maximum absolute error below 0.02 K.

Thermal management is a critical challenge in the design of chiplet-based 2.5D and 3D integrated systems. However, traditional simulation methods struggle with large-scale problems due to excessive time cost and memory consumption. In this article, we present a hybrid transfer model (HTM) to perform hierarchical thermal simulation with high efficiency and negligible accuracy loss. Initially, the chiplet-based system is partitioned into several modules based on their structural features, with each module further decomposed into multi-layered subdomains. In the subdomain-to-module stage, a novel HTM is developed to characterize the heat transfer property of each subdomain. These HTMs are then cascaded to compress the internal thermal information onto the interface of the module, thus representing the overall module characteristics with a small number of degrees of freedom. As for the system-to-module stage, the target modules are selected according to the requirements in different scenarios, and the impacts of the other modules are imposed on the interfaces in the form of equivalent boundary conditions. By this means, the solution domain is reduced from the entire system to the target modules successfully, contributing to a significant improvement in the computational efficiency. Numerical experiments on typical 2.5D and 3D chiplet-based integrated systems demonstrate that the proposed method achieves a 52× speedup with 11.7% memory cost compared to the commercial software, while maintaining a maximum absolute error below 10⁻⁴ K.

Thermal management plays an increasingly important role in the design of 3-D integrated circuits (ICs) and packages. To deal with the related thermal issues, efficient and accurate evaluation of the thermal performance is obviously essential. In this paper, an efficient approach with the flexible thermal conductance model (TCM) is presented for thermal simulation of 3-D ICs and packages. Firstly, the entire structure is partitioned and classified into two kinds of regions, named region of interest (ROI) and region of fixity (ROF). The ROI usually contains the key components in thermal designs while the ROF holds invariant thermal characteristics. Then, in order to represent the thermal impact of ROF on ROI, a novel technique based on the TCM is developed, which can be treated as the equivalent boundary condition of the ROI. By this means, the solution domain of the whole system is constrained to the ROI, which results in significant reduction of computational costs. Furthermore, in the representation of ROF, a flexible TCM with elegant rational expressions on the heat convection coefficient is proposed to deal with varying boundary conditions, which greatly expands the applicability of this method. The validity and efficiency of the proposed method is illustrated by the numerical examples, where a 138x speedup is achieved comparing with the commercial software.

Accurate and efficient simulation is essential for the thermal management of gallium nitride (GaN) high-electron-mobility transistors (HEMTs). However, conventional numerical approaches are usually time-consuming when dealing with transient thermal simulations with temperature-dependent parameters. To conquer this problem, we present a novel method based on the equivalent thermal conductance network (ETCN) model for efficient thermal simulation of GaN HEMTs. First, according to the temperature-dependent characteristics of the materials of the device, the entire structure is divided into region of variation (ROV) and region of fixity (ROF). Then, we decompose the transient response of ROF into a zero-input (ZI) and a zero-state (ZS) response based on the intrinsic property of linear time-invariant systems. After that, a novel ETCN model is developed for efficient transient simulation of GaN HEMTs. The principle of the ETCN model is to transform the impacts of the ROF on the ROV in the form of the equivalent thermal boundary conditions. By this means, we only need to focus on the ROV in the nonlinear iteration, enabling a significant reduction of degrees of freedom in solving the nonlinear equation and thus significantly improving the computational efficiency. In addition, the ETCN model is also available to handle the steady-state thermal problems. Several numerical examples are provided to validate the accuracy and efficiency of the proposed method. Compared with the conventional finite volume method, a speed-up of 105x is achieved by the ETCN model in simulating a typical multifinger GaN HEMT with microchannel cooling.

In the thermal design of 3-D integrated circuits (ICs) and packages, numerical simulation is extensively employed to investigate the impact of model parameters on hotspot temperature. However, conventional simulation approaches usually require plenty of computational resource and thus lead to expensive time cost for thermal designs. In this paper, we present a novel technique to efficiently and accurately conduct thermal simulation of 3-D ICs and packages, potentially reducing thermal design timeline from weeks to minutes. The proposed thermal resistance network derivative (TREND) model facilitates to focus the solution domain on the crucial regions for thermal designs and accelerate simulation without sacrificing accuracy. Also, the TREND model protects the internal details of chips and packages, which is quite suitable for modular thermal designs. The flexibility, accuracy, and efficiency of the proposed method are demonstrated through several numerical examples. Compared with the commercial software, a speed-up of 2695x is achieved in a typical thermal design case without the loss of accuracy.